Method for producing a solution consisting of a polymer containing recurrent azole units, solutions produced according to said method and use of the same

Abstract

The present invention relates to a method of preparing a solution of a polymer comprising recurring azole units, which comprises dissolving a sufficiently dried polymer comprising recurring azole units of the formula where the radicals Ar, Ar 1 and Ar 2 are tetravalent, divalent or trivalent aromatic or heteroaromatic groups and the radicals X, which are identical within a repeating unit, are each an oxygen atom, a sulfur atom or an amino group bearing a hydrogen atom, a group having 1–20 carbon atoms, preferably a branched or unbranched alkyl or alkoxy group, or an aryl group as further radical, in N,N-dimethylacetamide having a sufficiently low water content at a temperature above room temperature under an inert gas atmosphere, wherein a sufficiently dried polymer comprising recurring azole units of the formula (1) or (2) of which 90% by weight based on the total weight of the polymer comprising recurring azole units has a particle size of less than 1 mm is used.

1. A method of preparing a solution of a polymer comprising recurring azole units, which comprises dissolving a sufficiently dried polymer comprising recurring azole units of the formula                  
 wherein the radicals Ar, Ar 1  and Ar 2  are tetravalent, divalent or trivalent aromatic or heteroaromatic groups and the radicals X, which are identical within a repeating unit, are each an oxygen atom, a sulfur atom or an amino group bearing a hydrogen atom, a group having 1–20 carbon atoms, 
 in N,N-dimethylacetamide having a sufficiently low water content at a temperature of 250° C. or less under an inert gas atmosphere, wherein a sufficiently dried polymer comprising recurring awls units of the formula (1) or (2) of which 90% by weight based on the total weight of the polymer comprising recurring azole units has a particle size of less than 1 mm is used. 
 
     
     
       2. The method as claimed in  claim 1 , wherein X, which are identical within a repeating unit, are each an oxygen atom, a sulfur atom or an amino group bearing a hydrogen atom, a branched or unbranched alkyl, alkoxy group or an aryl group. 
     
     
       3. The method as claimed in  claim 1 , wherein the polymer comprising recurring azole units is firstly milled and then dried before dissolution in N,N-dimethylacetamide. 
     
     
       4. The method as claimed in  claim 1 , wherein the polymer comprising recurring azole units is dissolved at a temperature in the range from 160° C. to 250° C. 
     
     
       5. The method as claimed in  claim 3 , wherein the polymer comprising recurring azole units is dissolved at a temperature in the range from 180° C. to 220° C. 
     
     
       6. The method as claimed in  claim 4 , wherein a dried polymer comprising recurring azole units of the formula (1) or (2) which has a water content of less than 3% by weight based on the total weight of the polymer comprising recurring azole units is used. 
     
     
       7. The method as claimed in  claim 5 , wherein a dried polymer comprising recurring azole units of the formula (1) or (2) which has a water content of less than 3% by weight based on the total weight of the polymer comprising recurring azole units is used. 
     
     
       8. The method as claimed in  claim 1 , wherein said N,N-dimethylacetamide has a water content of less than 0.4% by weight based on the total weight of the N,N-dimethylacetamide. 
     
     
       9. The method as claimed in  claim 7 , wherein said N,N-dimethylacetamide has a water content of less than 0.4% by weight based on the total weight of the N,N-dimethylacetamide. 
     
     
       10. The method as claimed in  claim 1 , wherein the polymer comprising recurring azole units is dissolved over a period of less than 10 hours. 
     
     
       11. The method as claimed in  claim 1 , wherein a polymer comprising recurring benzimidazole units of the formula (3):                  
 wherein n is an integer greater than or equal to 10, is used. 
 
     
     
       12. A solution of a polymer comprising recurring azole units obtained by the method as claimed in  claim 1 , wherein, in head-space analysis of the solution of a polymer comprising recurring azole units at 50° C., the height of the peaks of dimethylamine and/or trimethylamine is less than 10% of the height of the DMAc peak. 
     
     
       13. A solution of a polymer comprising recurring azole units obtained by the method as claimed in  claim 1 , wherein the solution of a polymer comprising recurring azole units contains less than 3% by weight, based on the total weight of the polymer comprising recurring azole units, of material which can be separated off by filtration through a filter having a pore opening of 4 pm at 100° C. 
     
     
       14. The solution as claimed in  claim 13 , wherein, in head-space analysis of the solution of a polymer comprising recurring azole units at 50° C., the height of the peaks of dimethylamine and/or trimethylamine is less than 10% of the height of the DMAc peak. 
     
     
       15. The solution as claimed in  claim 14  which contains 25% by weight or less) based on its total weight, of polymer comprising recurring azole units.